三叠纪—侏罗纪之交(Triassic-Jurassic boundary,TJB)发生了三叠纪末的生物大灭绝(end-Triassic mass extinction,ETE),海洋和陆地生态系统都发生了不同程度的崩溃。而在陆地生态系统中,植物群首当其冲,但是该时段的植物群变化的详细...三叠纪—侏罗纪之交(Triassic-Jurassic boundary,TJB)发生了三叠纪末的生物大灭绝(end-Triassic mass extinction,ETE),海洋和陆地生态系统都发生了不同程度的崩溃。而在陆地生态系统中,植物群首当其冲,但是该时段的植物群变化的详细数据还相对缺乏。本文在新疆准噶尔盆地南缘郝家沟剖面TJB地层系统采样研究,来揭示该过程的植物群响应。根据孢粉属种组成及含量变化划分了3个孢粉组合,对古气候进行了重建。结果表明,准噶尔盆地南缘TJB的气候演变经历了湿热—湿冷—干热的转换过程。同时对ETE和TJB两个重要界线及灭绝发生的期次关系进行了讨论,由孢粉数据结合前人植物大化石、有机碳同位素地层曲线、生物标志化合物和Hg/TOC全球对比的结果,指示ETE和TJB可能分别位于郝家沟组43层底附近和八道湾组49层底附近;并推测三叠纪末陆地植被的灭绝在高纬度的准噶尔盆地记录到3个期次。在ETE与TJB之间地层中发现了与全球多处记录到的孢子含量激增一致的现象,推测该时期陆地生态系统的波动具有全球性。展开更多
非洲东南部晚更新世植被重建及对比研究有助于理解区域气候变化过程和驱动机制。本研究依托国际大洋发现计划IODP361航次科学任务所获取的U1477B海洋钻孔,对其上部4~37 m的沉积岩芯的79个样品进行了孢粉分析,重建了30~5 ka B.P.的区域...非洲东南部晚更新世植被重建及对比研究有助于理解区域气候变化过程和驱动机制。本研究依托国际大洋发现计划IODP361航次科学任务所获取的U1477B海洋钻孔,对其上部4~37 m的沉积岩芯的79个样品进行了孢粉分析,重建了30~5 ka B.P.的区域植被和气候变化历史。研究结果显示,钻孔岩芯整体以草本植物禾本科(Poaceae)和莎草科(Cyperaceae)花粉为主,平均约占75.5%;木本植物花粉较少,以罗汉松科(Podocarpaceae)、豆科(Fabaceae)、使君子科(Combretaceae)和红树科(Rhizophoraceae)等为主;孢粉组合记录了钻孔孢粉源区赞比西河流域的植被特征。在时间演化序列上,钻孔沉积物孢粉组合变化反映出明显的冰期-间冰期(全新世)的植被变化特征:末次冰期(30~17 ka B.P.)以禾本科、莎草科等草本花粉为主,平均约占82.2%,以草原/草甸植被占优势,推测在流域低海拔平原开阔草原广泛发育;罗汉松科为代表的山地森林在冰期也相对发育,指示了相对凉爽潮湿的气候环境;冰消期(17.0~10.5 ka B.P.)禾本科花粉保持稳定平均约占38.3%,而莎草科花粉含量在前期略有增加后呈持续下降的趋势,反映了低海拔流域逐渐干旱的气候条件,非洲山地森林植被罗汉松科花粉达到最高值,反映了高海拔山地森林植被出现扩张;全新世早-中期(10.5~5.0 ka B.P.)罗汉松科花粉占比减少,而干旱林地典型植被豆科、使君子科等花粉增加,指示全新世早-中期气候相对温暖干燥;而红树科花粉占比迅速增加,指示海平面迅速上升扩大了适宜红树林生长的沿海空间。末次冰期到全新世中期流域内植被组成变化指示末次冰期相对潮湿寒冷、冰消期降水减少、全新世早-中期温暖干燥的气候条件,降水变化与同纬度(18°S)日照强度变化有较好的一致性。因此,钻孔孢粉记录的植被演化及降水过程可能受控于当地夏季日照强度并且对北半球高纬度冷事件有一定的响应。展开更多
The Qaidam Basin, located in the northern margin of the Qinghai-Tibet Plateau, is a large Mesozoic-Cenozoic basin, and bears huge thick Cenozoic strata. The geologic events of the Indian- Eurasian plate-plate collisio...The Qaidam Basin, located in the northern margin of the Qinghai-Tibet Plateau, is a large Mesozoic-Cenozoic basin, and bears huge thick Cenozoic strata. The geologic events of the Indian- Eurasian plate-plate collision since -55 Ma have been well recorded. Based on the latest progress in high-resolution stratigraphy, a technique of balanced section was applied to six pieces of northeast- southwest geologic seismic profiles in the central and eastern of the Qaidam Basin to reconstruct the crustal shortening deformation history during the Cenozoic collision. The results show that the Qaidam Basin began to shorten deformation nearly synchronous to the early collision, manifesting as a weak compression, the deformation increased significantly during the Middle and Late Eocene, and then weakened slightly and began to accelerate rapidly since the Late Miocene, especially since the Quaternary, reflecting this powerful compressional deformation and rapid uplift of the northern Tibetan Plateau around the Qaidam Basin.展开更多
The Xining Basin on the northeastern Tibetan Plateau holds the longest continuous Cenozoic stratigraphic record in China.The sequence record contains considerable information on the history of Tibetan uplift and assoc...The Xining Basin on the northeastern Tibetan Plateau holds the longest continuous Cenozoic stratigraphic record in China.The sequence record contains considerable information on the history of Tibetan uplift and associated climatic change.In particular,high resolution n-alkane biomarker proxy and pollen records have been obtained from the Paleogene sediments of the Xiejia section of the basin.A combination of the n-alkane and palynological records reveals that the paleoclimate in the Xining Basin experienced a long-term cooling trend from 50.2 to 28.2 Ma with a distinctive ecological event spanning 37.5 to 32.7 Ma.Since this ecological event,a vertical zonation of vegetation from lowland arid grasses,to middle-elevation subtropical broad-leaf plants,to high-elevation coniferous trees was established.We interpret that these changes in climate and vegetation were probably responses to a combination of long term global cooling since the Eocene climatic optimum and uplift of the surrounding mountains on the northern Tibetan Plateau in the early Cenozoic.展开更多
The Eocene palaeovegetation landscape and palaeoclimate reconstructed from the pollen records in the Jiuquan Basin, northwest China provide some important information on the early uplift of the Tibetan Plateau and the...The Eocene palaeovegetation landscape and palaeoclimate reconstructed from the pollen records in the Jiuquan Basin, northwest China provide some important information on the early uplift of the Tibetan Plateau and the origin and evolution of the aridification in northwest China. The records show the arid-semiarid scrubs with open forest palynofloras controlled by the subtropical high existed in northwest China during the 40.2-33.4 Ma. Four pollen assemblages are found: Nitrariadites-Cheno-podipollis-Pinaceae assemblage (40.2-37.9 Ma) is followed by Chenopodipollis-Nitrariadites assemblage (37.9-34.6 Ma), Pinuspollenites & Abietineaepollenites-Chenopodipollis assemblage (34.6-33.9 Ma), and Chenopodipollis-Nitrariadites assemblage (33.9-33.4 Ma). The percentage of thermophilic types is in anti-correlation with that of the dry types, which means the palaeoclimate is relatively warmwet or cold-dry during most of that time. Such aridity may be related to the water vapor reduction and the planetary wind system movement northward in response to the cooling caused by small-ephemeral icesheets.展开更多
The red clay eolian sequence on the Chinese Loess Plateau (CLP) is an important archive for paleoclimate change from the late Miocene to Pliocene,and can provide significant information for the controversial problems ...The red clay eolian sequence on the Chinese Loess Plateau (CLP) is an important archive for paleoclimate change from the late Miocene to Pliocene,and can provide significant information for the controversial problems of East Asian monsoon evolution and its forcing mechanism.In this study,we present a pollen record from Baode,northern CLP.The record shows four stages of paleoecological evolution.From 5.6-4.4 Ma,a forest steppe ecosystem developed under an extremely warm period with high seasonal precipitation.Since 4.4 Ma,a drier episode occurred,which prompted parkland landscapes to develop.During 3.5-3.05 Ma,the environment changed to a rather open steppe ecosystem with a much cooler and drier climate.After 3.05 Ma,the vegetation evolved to forest steppe.Using the percentages of arboreal plants to mirror precipitation,and comparing with other published pollen data from the CLP,we find the existence of S-N directionality of the precipitation change and high percentage of arboreal plants in the entire CLP during the Early Pliocene,which suggest the CLP was characterized by a strong East Asian summer monsoon.The strong summer monsoon corresponds well to the low global ice volume,which may illuminate global climate mechanism for the summer monsoon evolution in the early Pliocene.展开更多
Two lacustrine sporopollen records obtained from the Qaidam Basin (in the non-monsoonal region) and the Linxia Basin (in the monsoonal transition zone) indicate that during the early Pleistocene open forest-steppe/ste...Two lacustrine sporopollen records obtained from the Qaidam Basin (in the non-monsoonal region) and the Linxia Basin (in the monsoonal transition zone) indicate that during the early Pleistocene open forest-steppe/steppe vegetation developed in the Qaidam Basin, while in the Linxia Basin an open cypress forest-steppe shifted to a conifer/conifer-steppe and then to open forest-steppe vegetation. Existing sporopollen records from the Chinese Loess Plateau (CLP) (in the monsoonal region) indicate that around the Sanmen Paleolake open forest-steppe shifted to pine/conifer-broadleaved mixed forest. The conifer cover then changed to a subtropical evergreen broadleaved forest distributed around the Nihewan Paleolake. These changes suggest that wetter conditions progressed from western China to the east, and the climate became more humid than that of today indicating a stronger Asian summer monsoon during the early Pleistocene.展开更多
文摘三叠纪—侏罗纪之交(Triassic-Jurassic boundary,TJB)发生了三叠纪末的生物大灭绝(end-Triassic mass extinction,ETE),海洋和陆地生态系统都发生了不同程度的崩溃。而在陆地生态系统中,植物群首当其冲,但是该时段的植物群变化的详细数据还相对缺乏。本文在新疆准噶尔盆地南缘郝家沟剖面TJB地层系统采样研究,来揭示该过程的植物群响应。根据孢粉属种组成及含量变化划分了3个孢粉组合,对古气候进行了重建。结果表明,准噶尔盆地南缘TJB的气候演变经历了湿热—湿冷—干热的转换过程。同时对ETE和TJB两个重要界线及灭绝发生的期次关系进行了讨论,由孢粉数据结合前人植物大化石、有机碳同位素地层曲线、生物标志化合物和Hg/TOC全球对比的结果,指示ETE和TJB可能分别位于郝家沟组43层底附近和八道湾组49层底附近;并推测三叠纪末陆地植被的灭绝在高纬度的准噶尔盆地记录到3个期次。在ETE与TJB之间地层中发现了与全球多处记录到的孢子含量激增一致的现象,推测该时期陆地生态系统的波动具有全球性。
文摘非洲东南部晚更新世植被重建及对比研究有助于理解区域气候变化过程和驱动机制。本研究依托国际大洋发现计划IODP361航次科学任务所获取的U1477B海洋钻孔,对其上部4~37 m的沉积岩芯的79个样品进行了孢粉分析,重建了30~5 ka B.P.的区域植被和气候变化历史。研究结果显示,钻孔岩芯整体以草本植物禾本科(Poaceae)和莎草科(Cyperaceae)花粉为主,平均约占75.5%;木本植物花粉较少,以罗汉松科(Podocarpaceae)、豆科(Fabaceae)、使君子科(Combretaceae)和红树科(Rhizophoraceae)等为主;孢粉组合记录了钻孔孢粉源区赞比西河流域的植被特征。在时间演化序列上,钻孔沉积物孢粉组合变化反映出明显的冰期-间冰期(全新世)的植被变化特征:末次冰期(30~17 ka B.P.)以禾本科、莎草科等草本花粉为主,平均约占82.2%,以草原/草甸植被占优势,推测在流域低海拔平原开阔草原广泛发育;罗汉松科为代表的山地森林在冰期也相对发育,指示了相对凉爽潮湿的气候环境;冰消期(17.0~10.5 ka B.P.)禾本科花粉保持稳定平均约占38.3%,而莎草科花粉含量在前期略有增加后呈持续下降的趋势,反映了低海拔流域逐渐干旱的气候条件,非洲山地森林植被罗汉松科花粉达到最高值,反映了高海拔山地森林植被出现扩张;全新世早-中期(10.5~5.0 ka B.P.)罗汉松科花粉占比减少,而干旱林地典型植被豆科、使君子科等花粉增加,指示全新世早-中期气候相对温暖干燥;而红树科花粉占比迅速增加,指示海平面迅速上升扩大了适宜红树林生长的沿海空间。末次冰期到全新世中期流域内植被组成变化指示末次冰期相对潮湿寒冷、冰消期降水减少、全新世早-中期温暖干燥的气候条件,降水变化与同纬度(18°S)日照强度变化有较好的一致性。因此,钻孔孢粉记录的植被演化及降水过程可能受控于当地夏季日照强度并且对北半球高纬度冷事件有一定的响应。
基金co-supported by the President Fund and Innovation Program of Chinese Academy of Sciences(no.:kzcx2-yw-104)the Chinese National Science Foundation grants(no.:40334038)the Science and Technology Key Project of Ministry of Education of China(no.:306016).
文摘The Qaidam Basin, located in the northern margin of the Qinghai-Tibet Plateau, is a large Mesozoic-Cenozoic basin, and bears huge thick Cenozoic strata. The geologic events of the Indian- Eurasian plate-plate collision since -55 Ma have been well recorded. Based on the latest progress in high-resolution stratigraphy, a technique of balanced section was applied to six pieces of northeast- southwest geologic seismic profiles in the central and eastern of the Qaidam Basin to reconstruct the crustal shortening deformation history during the Cenozoic collision. The results show that the Qaidam Basin began to shorten deformation nearly synchronous to the early collision, manifesting as a weak compression, the deformation increased significantly during the Middle and Late Eocene, and then weakened slightly and began to accelerate rapidly since the Late Miocene, especially since the Quaternary, reflecting this powerful compressional deformation and rapid uplift of the northern Tibetan Plateau around the Qaidam Basin.
基金supported by the National Natural Science Foundation of China (41021001,40920114001 and 40501079)the Knowledge Innovation Program of the Chinese Academy of Sciences (KZCX2-YW-Q09-04)
文摘The Xining Basin on the northeastern Tibetan Plateau holds the longest continuous Cenozoic stratigraphic record in China.The sequence record contains considerable information on the history of Tibetan uplift and associated climatic change.In particular,high resolution n-alkane biomarker proxy and pollen records have been obtained from the Paleogene sediments of the Xiejia section of the basin.A combination of the n-alkane and palynological records reveals that the paleoclimate in the Xining Basin experienced a long-term cooling trend from 50.2 to 28.2 Ma with a distinctive ecological event spanning 37.5 to 32.7 Ma.Since this ecological event,a vertical zonation of vegetation from lowland arid grasses,to middle-elevation subtropical broad-leaf plants,to high-elevation coniferous trees was established.We interpret that these changes in climate and vegetation were probably responses to a combination of long term global cooling since the Eocene climatic optimum and uplift of the surrounding mountains on the northern Tibetan Plateau in the early Cenozoic.
基金the National Key Program for Developing Basic Sciences (Grant No. 2005CB422001)the National Science Foundation of China (Grant Nos. 40334038, 40421101)the President Fund of Chinese Academy of Sciences
文摘The Eocene palaeovegetation landscape and palaeoclimate reconstructed from the pollen records in the Jiuquan Basin, northwest China provide some important information on the early uplift of the Tibetan Plateau and the origin and evolution of the aridification in northwest China. The records show the arid-semiarid scrubs with open forest palynofloras controlled by the subtropical high existed in northwest China during the 40.2-33.4 Ma. Four pollen assemblages are found: Nitrariadites-Cheno-podipollis-Pinaceae assemblage (40.2-37.9 Ma) is followed by Chenopodipollis-Nitrariadites assemblage (37.9-34.6 Ma), Pinuspollenites & Abietineaepollenites-Chenopodipollis assemblage (34.6-33.9 Ma), and Chenopodipollis-Nitrariadites assemblage (33.9-33.4 Ma). The percentage of thermophilic types is in anti-correlation with that of the dry types, which means the palaeoclimate is relatively warmwet or cold-dry during most of that time. Such aridity may be related to the water vapor reduction and the planetary wind system movement northward in response to the cooling caused by small-ephemeral icesheets.
基金supported by the National Natural Science Foundation of China(40871098,40771214 and 40920114001) the Knowledge Innovation Program of the Chinese Academy of Sciences (KZCX2-YW-Q09-04)
文摘The red clay eolian sequence on the Chinese Loess Plateau (CLP) is an important archive for paleoclimate change from the late Miocene to Pliocene,and can provide significant information for the controversial problems of East Asian monsoon evolution and its forcing mechanism.In this study,we present a pollen record from Baode,northern CLP.The record shows four stages of paleoecological evolution.From 5.6-4.4 Ma,a forest steppe ecosystem developed under an extremely warm period with high seasonal precipitation.Since 4.4 Ma,a drier episode occurred,which prompted parkland landscapes to develop.During 3.5-3.05 Ma,the environment changed to a rather open steppe ecosystem with a much cooler and drier climate.After 3.05 Ma,the vegetation evolved to forest steppe.Using the percentages of arboreal plants to mirror precipitation,and comparing with other published pollen data from the CLP,we find the existence of S-N directionality of the precipitation change and high percentage of arboreal plants in the entire CLP during the Early Pliocene,which suggest the CLP was characterized by a strong East Asian summer monsoon.The strong summer monsoon corresponds well to the low global ice volume,which may illuminate global climate mechanism for the summer monsoon evolution in the early Pliocene.
基金supported by the President Fund and Innovation Program of the Chinese Academy of Sciences (KZCX2-YW-Q09-04)the National Natural Science Foundation of China (40871098,40920114001 and 40802041)the National Basic Research Program of China (2005CB422000)
文摘Two lacustrine sporopollen records obtained from the Qaidam Basin (in the non-monsoonal region) and the Linxia Basin (in the monsoonal transition zone) indicate that during the early Pleistocene open forest-steppe/steppe vegetation developed in the Qaidam Basin, while in the Linxia Basin an open cypress forest-steppe shifted to a conifer/conifer-steppe and then to open forest-steppe vegetation. Existing sporopollen records from the Chinese Loess Plateau (CLP) (in the monsoonal region) indicate that around the Sanmen Paleolake open forest-steppe shifted to pine/conifer-broadleaved mixed forest. The conifer cover then changed to a subtropical evergreen broadleaved forest distributed around the Nihewan Paleolake. These changes suggest that wetter conditions progressed from western China to the east, and the climate became more humid than that of today indicating a stronger Asian summer monsoon during the early Pleistocene.
